Several board and panel products have been used or proposed for use in the construction of insulating curtain walls. U.S. Pat. No. 3,389,518 discloses constructing a curtain wall by adhering a plastic foam board layer to a supporting wall, adhering a reinforcing layer, consisting of a cemetitious material and glass fabric, over the foam board layer, and finally applying a finish coating of a mixture of a mineral aggregate and a binder. A less labor intensive method would be advantageous, with respect to this prior method.